Tetrahedrites, a class of naturally-occurring sulfosalts, recently emerged as interesting thermoelectric materials due to their semiconducting electronic properties combined with glass-like thermal transport. Here, we demonstrate that the high thermoelectric performance of synthetic tetrahedrites can be maintained while being mixed with tetrahedrite minerals. The combination of ball-milling and spark plasma sintering yields chemically-homogeneous, dense polycrystalline samples with thermoelectric performance equivalent to those obtained in purely synthetic compounds with peak ZT values of 0.6 at 623 K. While ball-milling significantly lowers the crystallite size, a complete solid solution between both types of tetrahedrites is only achieved through the sintering process. Not only do these findings confirm interesting prospects for the direct use of natural ores in the preparation of tetrahedrites, but they also further evidence the importance of the chemical compositions of the two initial tetrahedrites on the optimization of the thermoelectric properties of the final compound.